The present invention is directed, in general, to a wafer cleaning apparatus and, more specifically, to an apparatus and method for maintaining semiconductor wafer cleaning brushes in a state of readiness for wafer cleaning.
During semiconductor manufacturing, several processes create debris that is best removed by mechanical means, specifically, after silicon polishing, laser scribing and chemical/mechanical polishing. Silicon polishing is performed after a silicon ingot is cut into wafers to prepare the wafers for further precessing. Laser scribing is the process by which identifying numbers are scribed into the wafer, and chemical/mechanical polishing uses an abrasive slurry to planarize the wafer surface. Each of these processes creates debris that may cling to the wafer surface and present a potential contamination hazard. With the high cost of semiconductor manufacturing and intense competition among manufacturers, every effort must be made to minimize any contamination hazard.
Following these processes, the surfaces of the semiconductor wafer are best cleaned of any residual debris by passing the wafer between two rollers equipped with polyvinyl alcohol (PVA) brushes. While ammonium hydroxide or dilute hydrofluoric acid is used for semiconductor wafer cleaning the PVA brushes may also be kept wetted with de-ionized water to provide the high quality surface necessary for removing debris. While in use, the combination of brush rotation and pressure applied to the semiconductor wafer through the brushes flexes the PVA material and keeps the brushes in proper condition for cleaning additional wafers.
However, the brushes are idle when there are no wafers being cleaned and, as a consequence, the brushes lose their resilience, thereby suffering a loss of particle removal efficiency. Therefore, before the brushes may be used on production-quality wafers, xe2x80x9cdummyxe2x80x9d or warmup wafers, i.e., wafers that will not be used to produce commercially useable chips, are run through the cleaners to condition the PVA brushes and restore their resilience. As few as 10 percent to as many as 20 percent of the wafers in small lots passing through the cleaner may be dummy wafers. Of course, this requires machine time, manpower, and additional chemicals to restore the brushes resilience, factors that would better be spent on wafer production and that ultimately increase the costs of production of semiconductor wafers and chips.
Accordingly, what is needed in the art is an apparatus and method that requires minimal to no investment of technical manpower for maintaining cleaning brushes in a virtually constant state of readiness to clean semiconductor wafers.
To address the above-discussed deficiencies of the prior art, the present invention provides a method of manufacturing an integrated circuit using a cleaning brush and a cleaning brush conditioning apparatus. In one embodiment, the cleaning brush conditioning apparatus comprises a conditioning bar and a load cell coupled to the conditioning bar. The load cell is configured to force the conditioning bar against the cleaning brush.
In another embodiment, the conditioning bar is cylindrical and has a longitudinal axis and the conditioning bar is capable of rotating about the longitudinal axis. The conditioning bar, in other embodiments, may comprise a surface material of TEFLON(copyright) (i.e., synthetic resinous fluorine), silicon, silicon nitride, ceramic, or silicon carbide. In a particularly advantageous embodiment, the cleaning brush is a semiconductor wafer cleaning brush.
In an alternative embodiment, the cleaning brush conditioning apparatus further comprises a dispenser containing a cleaning agent. The dispenser is coupled to the conditioning bar and configured to deliver the cleaning agent to the cleaning brush. In a further aspect, the cleaning agent may be deionized water, ammonium hydroxide, dilute hydrofluoric acid, other suitable chemical solvents, or surfactants.
The cleaning brush conditioning apparatus, in another embodiment, may further comprise a resiliency or indentation sensor coupled to the cleaning brush and configured to sense a resiliency of the cleaning brush, and a controller coupled to the load cell and to the resiliency sensor. The controller is configured to activate the load cell when the resiliency is less than a nominal resiliency. In yet another embodiment, the load cell is capable of applying a variable force.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.